(a) Field of the Invention
The present invention relates to an apparatus and a method for generating a ramp waveform.
(b) Description of the Related Art
A plasma display device uses a plasma display panel that displays texts or images by using plasma generated by gas discharge.
In the plasma display device, a rising ramp waveform of gradually increasing the voltage of an electrode and a falling ramp waveform of gradually decreasing the voltage of the electrode during a reset period so as to form uniform wall charges for all cells while inducing the generation of continuous dark discharge are applied to the electrode. The slope of the ramp waveform serves as an important factor to determine the image quality of a plasma display panel.
In the related art, during a manufacturing process, a variable resistor connected between a gate of a transistor and a gate driver of the transistor is manually adjusted to control the slope of the ramp waveform. However, such a method may complexify the manufacturing process and may increase an adjustment deviation and much additional process cost resulting from a manual work. Further, the slope of the ramp waveform is influenced by a variation of a power semiconductor switch, a variation of reference voltage, and temperature characteristics. However, only by using the method of manually adjusting the variable resistor during the manufacturing process, it is impossible to accurately adjust the slope of the ramp waveform which varies by an internal factor or an external factor.
As a technology to solve the problem, a technology of detecting image information relating to the slope of the ramp waveform and thereafter, automatically generating the slope of the ramp waveform on the basis of the detected image information has been proposed. However, the technology has a feedback algorithm for detecting the image information relating to the slope of the ramp waveform, which is significantly complicated and requires many elements such as an analog-to-digital converter (ACD) or a digital-to-analog converter (DAC), a comparator, a photocoupler, and the like.
Another related art which controls the slope of the ramp waveform controls the slope of the ramp waveform by detecting voltage applied to the transistor and providing a feedback gain for controlling the gate of the transistor in an error amplifier depending on the voltage applied to the transistor. However, although such a method may generate a stable ramp waveform regardless of internal and external factors, but it requires a bootstrap capacitor having high capacitance in order to detect the voltage applied to the transistor and cannot change the slope of the ramp waveform.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.